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Arbitrary IIR Filter Design for Audio Applications

Digital infinite impulse response (IIR) filters are popular in audio signal processing applications because they typically have a much lower computational cost than finite impulse response (FIR) filters designed to the same specifications. However, IIR filter design is difficult, particularly for arbitrary frequency responses that span multiple octaves, as is common in audio. A recent technique known as frequency warping offers a new way to design arbitrary IIR filters with much greater accuracy than before.

Dr. Kite will review existing IIR design methods, and show how frequency warping is related to the popular bilinear transform. Using a multi-band approach pioneered by Bank, he will show how IIR filters can be designed for the entire audio band with accuracy limited only by filter complexity. Dr. Kite will demonstrate a 30-pole filter designer controlled via a GUI, and show how high-order filters can alleviate common audio headaches such as the ragged frequency responses of loudspeakers.

Speaker

Dr. Thomas Kite received his BS Physics degree (1993) from Oxford University, MSEE degree (1995) from UT Austin and PhDEE degree (1998) from UT Austin. He has industrial experience in analog/digital hardware design, hardware/software design, and embedded digital signal processors. Since fall 1998, he has been with Audio Precision in Portland, Oregon, where he is currently Vice President of Engineering. He can be reached at tomk@audioprecision.com.